The 1908 Tunguska cosmic body (TCB) explosion: Role of hydrogen thermonuclear explosion in support of cometary hypothesis

If the 1908 Tunguska cosmic body (TCB) explosion involved a comet, compressional heating of the comet was expected to create hydrogen and deuterium plasma. The velocity distribution of protons and deuterons in this plasma is not expected to be the Maxwell-Boltzmann distribution. It is shown that the use of a generalized momentum distribution leads to substantial increases of deuteron fusion rates and that a thermonuclear explosion may compete with a thermo-chemical explosion. Therefore, it may be possible that a thermo-chemical explosion induced a hydrogen thermonuclear explosion and both the thermo-chemical and thermonuclear explosions occurred in the 1908 Tunguska event. Experimental tests of this hypothesis are proposed.     

Isotope variations of hydrogen, carbon and nitrogen in florae from the Schirmacher Oasis, East Antarctica

Comparative biochemical and isotope-chemical investigations of cosmopolitical plants open up ways of obtaining parameters from different parts of the Earth which are characterised by variations in the habitat due to different environments. As an Antarctic oasis, the Schirmacher Oasis disposes of adequate favourable ecological conditions for the growth of lower plants. In the present paper, results of isotope studies of lichens, mosses and algae of the Schirmacher Oasis are given and peculiarities of the habitats which influence the isotope contents of the plants are discussed.     

Isotope variations of hydrogen,carbon and nitrogen in florae from the Schirmacher Oasis,East Antarctica

Comparative biochemical and isotope-chemical investigations of cosmopolitical plants open up ways of obtaining parameters from different parts of the Earth which are characterised by variations in the habitat due to different environments. As an Antarctic oasis, the Schirmacher Oasis disposes of adequate favourable ecological conditions for the growth of lower plants.

In the present paper, results of isotope studies of lichens, mosses and algae of the Schirmacher Oasis are given and peculiarities of the habitats which influence the isotope contents of the plants are discussed.     

Isotope Anomalies of Carbon,Hydrogen and Nitrogen in Peat from the Area of the Tunguska Cosmic Body Explosion (1908)

Abstract

Peat profiles from the area of the Tunguska explosion epicentre indicate significant carbon and hydrogen isotopic effects which are clearly associated with the zone of the 1908 “catastrophe”, and which cannot be attributed to any known terrestrial processes. We explain them with the presence of extraterrestrial matter similar to carbonaceous chondrites or, more probably, to cometary matter. Initial data on nitrogen content and its isotope composition are consistent with the assumption of acid rainfall following the passage and explosion of the Tunguska cosmic body, as is known to have occurred during the Cretaceous-Tertiary boundary.     

Adsorption and desorption of ammonia,hydrogen, and nitrogen on ruthenium (0001)

The adsorption of ammonia, hydrogen, and nitrogen on a Ru(0001) surface have been investigated by Auger electron spectroscopy, low-energy electron diffraction, and thermal flash desorption. The adsorption of ammonia on Ru(0001) can be divided into a low temperature mode (100 K) and a higher temperature mode (300–500 K). For a crystal temperature of 100 K the ammonia adsorbs into two weakly bound molecular γ states with s = 0.2. The ammonia desorbs as NH₃ molecules with desorption energies of 0.32 and 0.46 eV. At 300–500 K adsorption occurs via an activated process with a low sticking probability (s ? 2 × 10^?4).This adsorption is accompanied by dissociation and formation of an apparent (2 × 2) LEED pattern. Hydrogen adsorbs readily (s = 0.4) on Ru(0001) at 100 K and desorbs with 2nd order kinetics in the temperature range 350–450 K. Nitrogen does not appreciably adsorb on Ru(0001) even at 100 K; maximum nitrogen coverage obtained was estimated to be <2% of a monolayer. Changes in the ammonia flash desorption spectra after hydrogen preadsorption at 100 K will be discussed.     

Isotope effects in the interaction of hydrogen and deuterium with a rhodium (110) surface

The adsorption of H₂ and D₂ on a Rh (110) surface at 100 K leads to a sequence of ordered phases, among others 1×2 phases at _H =0.5 and at _H =1.5 which likely involve a partial surface reconstruction consisting of a small perpendicular displacement of Rh surface atoms. The structure of the adsorbate phases is strongly correlated with the binding energy of the adsorbed phases. Three H (D) binding states (₁,₂ and) are populated at saturation as determined by thermal desorption spectroscopy (TDS). Whereas the peak temperature of the state is invariant with the hydrogen isotope, the D ₁ state appears at a 8 Klower and theD ₂ state at a 5 Khigher temperature than the respective H states. Generally the D phases exhibit a better long-range order than the H phases. The rate of adsorption is identical for the first three adsorbed phases but D₂ adsorbs appreciably faster in the 1×2–3H and the final l×1–2H phases.Zero point energy effects as well as a H coverage dependent local interaction model could account for the observed effects.     

Interaction of oxygen, carbon monoxide and nitrogen with (001) and (110) faces of molybdenum

A combination of low-energy electron diffraction and retarding potential measurements was employed to study gaseous adsorption on atomically clean (001) and (110) Mo single crystal surfaces. Adsorption of oxygen on the (001) surface at room temperature occurred with a sticking coefficient close to unity and produced a large increase in work function and appreciable changes in the intensity distributions of the integral order diffraction beams, without the appearance of any new diffraction beams. These results indicate that a surface monolayer of oxygen was formed with a unit mesh having the same dimensions as that of the underlying molybdenum surface. Exposures above 6 × 10⁻³ Torr-sec produced a uniform decrease in intensities, thus indicating a second monolayer with amorphous structure. On heating, two additional surface structures were observed, characterized by one-half and one-third order beams, respectively. A clean surface was obtained by heating above 1100 °C. An exposure of 1 to 7 × 10⁻⁷ Torr-sec of oxygen for the (110) face resulted in two types of patterns characteristic of lattices with one-quarter and one-half the surface density of the (110) Mo face, with an increased work function accompanying the latter pattern. Exposure of the clean surface at 400 to 800 °C produced similar patterns of enhanced intensities with no increase in work function. Possible models are discussed. It is concluded that place exchange models account for these results, as well as the one-half and one-third order structures on the (001) face, in a more satisfactory manner than adsorption above the surface. An exposure to 10⁻⁵ Torr-sec produced a monolayer coverage with a unit mesh similar to that of the molybdenum substrate. Additional exposure resulted in further amorphous adsorption. Adsorption of CO produced changes in the intensity distributions, with the appearance of no new maxima, for both (001) and (110) Mo surfaces. Nitrogen, at an exposure of 3 × 10⁻³ Torr-min did not adsorb on either the (001) or (110) Mo surface, but when dissociated by electron impact it adsorbed on both Mo surfaces with the same dimensions of unit mesh as those of the Mo substrates and with an increase in work function of 1.05 eV for the (001) and 0.05 eV for the (110) surface.     

Adsorption of carbon monoxide,oxygen, hydrogen,nitrogen, ethylene and benzene on an iridium (110) surface; Correlation with other iridium crystal faces

The interaction of CO, O₂, H₂, N₂, C₂H₄ and C₆H₆ with an Ir(110) surface has been studied using LEED, Auger electron spectroscopy and flash desorption mass spectroscopy. Adsorption of oxygen at 30°C produces a (1× 2) structure, while a c(2 × 2) structure is formed at 400°C. Two peaks have been detected in the thermal desorption spectrum of oxygen following adsorption at 30°C. The heat of adsorption of hydrogen is slightly higher on Ir(110) than on Ir(111). Adsorption of carbon monoxide at 30°C produces a (2 × 1) surface structure. The main CO desorption peak is found around 230, while two other desorption peaks are observed around 340 and 160°C. At exposures between 250 and 500°C carbon monoxide adsorption yields a c(2 × 2) structure and a desorption peak around 600°C. Carbon monoxide is adsorbed on an Ir(110) surface partly covered with oxygen or carbon in a new binding state with a significantly higher desorption temperature than on the clean surface. Adsorption of nitrogen could not be detected on either clean or on carbon covered Ir(110) surfaces. The hydrocarbon molecules do not form ordered surface structures on Ir(110). The thermal desorption spectra obtained after adsorption of C₆H₆ or C₂H₄ are similar to those reported previously for Ir(111) consisting mostly of hydrogen. Heating the (110) surface above 700°C in the presence of C₆H₆ or C₂H₄ results in the formation of an ordered carbonaceous overlayer with (1 × 1) structure. The results are compared with those obtained previously on the Ir(111) and Ir(755) or stepped [6(111) × (100)] surfaces. The CO adsorption results are discussed in relation to data on similar surfaces of other Group VIII metals.     

Uptake,transport, and release of hydrogen from Pd(100)

Understanding the interactions of hydrogen atoms with the surface and the subsurface regions of Pd is critical to the development of advanced energy technologies for hydrogen storage, hydrogen separations, and catalytic conversion processes. While many of the physical and chemical characteristics of the H₂–Pd system are known, the kinetics and thermodynamics of H atom absorption into the bulk, transport from the bulk back to the surface, and desorption from the surface remain unclear. In this work, the kinetics of D₂ release from Pd following exposure to D₂ over a range of pressures and temperatures were measured using temperature programmed desorption. To accurately simulate the kinetics of D₂ release, the continuum-based model of Mavrikakis, et al. (J. Chem. Phys 105, 8398, 1996) was extended to include activation barriers for desorption and transport that depend on D atom concentration in the surface, subsurface and bulk regions of the Pd. The use of concentration dependent barriers improves the ability of the model to predict the hydrogen uptake and release kinetics observed across temperatures ranging from 100 to 600 K.     

Incorporation of nitrogen into amorphous-hydrogenated carbon (diamond-like) films

Nitrogen-doped amorphous hydrogenated carbon films (a-C:H) were prepared by mixing nitrogen gas and benzene during dc plasma discharge deposition. The growth rate of the film decreases strongly with increasing nitrogen content in the mixture. The nitrogen concentration in the films was determined by nuclear reaction analysis (NRA) and Auger electron spectroscopy (AES) using suitable calibration samples. The results of AES measurements are generally consistent with NRA values. Nitrogen incorporation in the a-C:H films shows pronounced doping effects as reflected in their optical and electrical properties.Dedicated to Professor J. P. F. Sellschop for his 60^th birthday     

Isotope effects in the Lyman and Werner systems of molecular hydrogen

A prototype model of amphiphilic discotic binary solutions is proposed, and its statistical mechanics investigated by Monte Carlo computer simulation procedures. Data are presented from a large number of simulations, over 50 separate systems in all, carried out at a single relatively low pressure but covering almost the entire temperature-composition range of phase space beyond the melting line, including successful simulations of equilibrated cluster distributions throughout the isotropic solution phase. These data are in agreement with the well known theory of linear aggregation, but a major surprise is found in that the associated equilibrium constant possesses a strong concentration dependence at low temperature. The global aggregation behaviour is described in detail and discussed in the context of the standard state that is usually invoked when applying linear aggregation theory to experimental systems. It is concluded that as the temperature decreases the ideal behaviour of these cluster distribution data shows more and more influence from the nearby infinite polydispersity limit. At sufficiently high surfactant concentration our model discotic solutions melt first into partially ordered states of aligned aggregates (columns of discs) surrounded by liquid solvent. Both a nematic phase and a hexagonally ordered columnar phase are observed. Simulation procedures are used to investigate the phase behaviour and especially the microscopic structure of these lyotropic liquid crystal systems. The thermodynamic behaviour of our prototype molecular model shows a qualitative resemblance to experimental results obtained from aqueous solutions of the discotic amphiphile known as TP6EO2M.     

Adsorption and coadsorption of carbon monoxide and hydrogen on Pd(111)

The adsorption and coadsorption of CO and H₂ have been studied by means of thermal desorption (TD) and electron stimulated desorption (ESD) at temperatures ranging from 250 to 400 K. Three CO TD states, labelled as β₂, β₁, and β₀ were detected after adsorption at 250 K. The population of β₂ and β₁ states which are the only ones observed upon adsorption at temperatures higher than 300 K was found to depend on adsorption temperature. The correlation between the binding states in the TD spectra and the ESD O⁺ and CO⁺ ions observed was discussed. Hydrogen is dissociatively adsorbed on Pd(111) and no ESD H⁺ signal was recorded following H₂ adsorption on a clean Pd surface. The presence of CO was found to cause an appearance of a H⁺ ESD signal, a decrease of hydrogen surface population and an arisement of a broad H₂ TD peak at about 450 K. An apparent influence of hydrogen on CO adsorption was detected at high hydrogen precoverages alone, leading to a decrease in the CO sticking coefficient and the relative population of CO β₂ state. The coadsorption results were interpreted assuming mutual interaction between CO and H at low and medium CO coverages, the “cooperative” species being responsible for the H⁺ ESD signal. Besides, the presence of CO was proved to favour hydrogen penetration into the bulk even at high CO coverage when H atoms were completely displaced from the surface.     

Ultrastructure and morphometry of the egg of Psorophora albigenu Lutz, 1908 (Diptera: Culicidae)

Eggs of Psorophora albigenu were analyzed by light and scanning electron microscopy. Eggs were laid singly and were black and elliptical in outline. A length of approximately 586.4 ± 10.83 μm, a width of 172.3 ± 8.09 μm (n=30), and an egg index (length/width ratio) of 3.33 were observed. The anterior extremity tapered abruptly from a width of 64.9 μm, while such tapering was more gradual at the posterior extremity from a width of 77.4 μm. The ventral surface of the chorionic coating presented cells with tubular aspect containing tubercles in rows with a density of 9-16 tubercles per cell. These tubercles presented two different sizes, with the largest measuring 7.87 ± 01.58 μm and the smallest measuring 0.71 ± 0.53 μm (n=30) in longitudinal diameter. The micropyle orifice was very evident, with a diameter of 3.36 μm. The morphometric characteristics of Ps. albigenu obtained in this study were distinct from those of other species of the Psorophora genus, including Psorophora varipes which has been considered for a long time to be synonymous with Ps. albigenu.     

(1, 1) Supergravity effective action and anomalies

I calculate the effective action of the (1, 1) supergravity using the superspace Feynman method. I discuss the dependence of the result on the conformal degree of freedom and trace the regularization arbitrariness. Trace and gravitational anomalies are discussed and their connection to string theories is stressed.     

Comparison between the adsorption properties of Pd(111) and PdCu(111) surfaces for carbon monoxide and hydrogen

Thermal desorption spectroscopy and LEED have been used to investigate the interaction of CO and hydrogen with a Pd_0.75Cu_0.25(111) single crystal surface with surface composition of about Pd_0.7Cu_0.3. The main objective was to make a comparison with the previously studied Pd_0.67Ag_0.33(111) (surface composition Pd_0.1Ag_0.9) and Pd(111) surfaces. In addition, the effect of preadsorbed H on subsequent CO dosage and the effect of adsorbed CO on postdosed hydrogen are described. Marked differences were found in the adsorption behaviour of the three surfaces towards CO and hydrogen. The maximum amount of H and CO that can be adsorbed at 250 K and pressures below 10⁻⁹ mbar is much lower on the PdCu surface than expected on the basis of the surface composition. This effect appears to be caused by a low heat of adsorption of hydrogen and CO and Pd singlet sites. Arguments are presented that singlet Pd sites or isolated Pd atoms in a Cu or Ag matrix are able to trap and dissociate the hydrogen molecule at 250 K. The CO desorption spectra are not influenced by pre- or postexposed hydrogen. Adsorbed CO hampers the uptake of hydrogen upon subsequent exposure to hydrogen. Postdosed CO causes adsorbed H adatoms to move to the bulk (adsorbed H). CO exposure at 250 K results in a very broad desorption plateau between 310 and 425 K with hardly discernable maxima. The results can be explained in terms of the size and relative concentration of the various Pd sites present on the surface (triplet, doublet and singlet sites). It can be concluded that for Pd (111) the heat of adsorption of both CO and H differ appreciably for the triplet, doublet and singlet sites. The effect of site has a larger contribution to the decrease of the heat of adsorption with coverage than the effect of lateral interaction in the adlayer. For Pd(111), PdCu(111) and PdAg(111) the effect of the available Pd sites is the major effect that determines the heat of adsorption, followed by the effect of lateral interaction and for the alloy surfaces the electronic or ligand effect.     

Studies of continuum radiation from nitrogen,oxygen and carbon dioxide plasmas in the vacuum ultraviolet region

The spectral distribution of the radiation intensities of nitrogen, oxygen and carbon dioxide plasmas have been measured at atmospheric pressure and temperatures of 10,000–13,000 K within the spectral range 110–250 nm. Analysis of our results and literature data shows a continuum produced by the formation of negative ions and the importance of photoattachment in the total radiation intensities of nitrogen and oxygen plasmas. Photodetachment cross sections of N^- and O^- have been determined. Calculations were made on the assumption of LTE in the plasma. The applicability of this assumption under the conditions of the experiments is discussed.     

Nuclear charge radii from X-ray transitions in muonic atoms of carbon,nitrogen and oxygen

Energies of muonic X-rays of the K-series of carbon, nitrogen and oxygen have been measured with an accuracy of about 15 eV. Root mean square radii of the nuclear charge distributions were deduced. The results 2.49±0.05 fm for carbon, 2.55±0.03 fm for nitrogen and 2.71 ±0.02 fm for oxygen are in good agreement at comparable accuracy with recent electron scattering data.